In conventional instrument assemblies, a meter mounting panel which covers the front section of the assembly except portions where dial boards of the meters are exposed is constructed of an opaque material such as a darkly colored plastic and is not illuminated in any way. Thus, the instrument assembly as a whole tends to give a gloomy impression. Further, a problem with such an opaque panel is that it appears black in the nighttime, even if it is offered in a relatively bright color, presenting a totally different contrast in color and illumination to the meters, compared with the contrast in the daytime.